Rare Sight: Giant Asteroid Eclipses Bright Star Regulus This Week

The bright star Regulus will vanish behind the asteroid 163 Erigone for several seconds on the morning of March 20, 2014, for well-placed skywatchers. The star is located in the "sickle" of the constellation Leo, the Lion.Credit: Akira Fujii / Sky & Telescope magazine

A rare cosmic sight will grace the night sky this week when the huge the asteroid Erigone passes in front of the bright star Regulus, as seen from Earth, on the night of March 19 and 20. The event, which is only visible from a narrow swath across the northeastern North America, offers a celestial treat for skywatchers there, and citizen scientists are wanted to help track the event.

The predicted occultation path of the bright star Regulus by the asteroid 163 Erigone on March 20, 2014 is shown in this map by Geoff Hitchcox/IOTA using Google Maps. The blue lines show the outer edges of the zone where Regulus will be blacked out if the prediction is perfect. Astronomers expect the prediction to be closely on target; the actual shadow path is almost sure to fall somewhere between the slightly wider uncertainty lines (within the red lines to 68-percent probability, within the gray lines to 95-percent probability).Credit: Geoff Hitchcox / IOTA / Google Maps

The asteroid Erigone (eh-RIG-uh-nee) will eclipse the star Regulus for between 14 seconds and up to two minutes (the time depends on viewing location) depending on where you are — and will take place around 2:06 a.m. EDT (0606 GMT). It will be visible in New York City as well as parts of Long Island, New Jersey, Connecticut, upstate New York, and Ontario.

Regulus is the brightest star in the constellation Leo and is bright enough to spot with the naked eye. To find it, go outside around 2 a.m. and look at the moon. Put your arms out straight out on either side of your body. In this position, Regulus is directly above the observer's right hand at about the same height in the moon.

"Regulus shines right through moonlight and light pollution that's in the sky — even the light pollution over a city like New York," said Alan MacRobert, a senior editor at Sky & Telescope magazine, in a statement. "Just be sure to shield your eyes against any glary lights, and Regulus should be easy to find."

This event is called an occultation, which comes from the Latin word for "hide." In a cosmic first, this is the only time yet that an asteroid occultation occurred in such a populous region.

This Stellarium sky map shows the position of the star Regulus in the constellation Leo as it will appear in the southwestern sky, 90 degrees to the right of the moon, at 2 a.m. EDT on March 20, 2014. Regulus will appear roughly as high as the moon, and be the brightest star in the area.Credit: IOTA / Stellarium / Sky & Telescope

The International Occultation Timing Association is asking amateurs to keep tabs on when the star disappears from view, and for how long. This can be recorded with your eyes only, or by using a DSLR camera in movie mode, or even fancier equipment. More on how to participate is available at occultations.org/Regulus2014.

Once the results are tabulated from various locations, astronomers can better estimate how big Erigone is, and its shape. This is a calculation that is usually not possible unless a spacecraft whizzes close by the asteroid itself.

The times of the occulation depend on where you are located. Generally speaking, it will be at 2:06 a.m. in New York City, 2:07 a.m. in upstate New York, and 2:08 a.m. north of Lake Ontario.

Erigone is about 45 miles (72 kilometers) across and orbits the sun about 110 million miles (117 million kilometers) from Earth, in the asteroid belt that is roughly between Mars and Jupiter. The asteroid is about 26,000 times fainter than Regulus (magnitude 12.4), so it can't be seen with amateur telescopes.

Even if you're not directly in the line of fire, so to speak, the consortium encourages anyone between the Carolinas to Nova Scotia to Winnipeg to keep an eye out. That's because if Erigone has a smaller asteroid with it, the other asteroid could also blot out Regulus sometime between 2 a.m. to 2:12 a.m. EDT (0600 to 0612 GMT).